Electrical wave filter



June 27, 1939. H. o. PETERSON ELECTRICAL WAVE FILTER Original Filed April 2, 1934 INVENTOR. HAROL PETERSON ATTORNEY.

Patented June 27, 1939 ELECTRICAL WAVE FILTER Harold 0. Peterson, Riverhead, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Original application April 2, 1934, Serial No. 718,738. Divided and this application March 10, 1938, Serial No. 195,051

. 11 Claims.

The present invention is a division of my application Serial No. 718,738, filed April 2, 1934, and. relates to ultra short wave electrical wave filters.

One of the objects of my'present invention is to provide an electrical wave filter composed of series and shunt elements, at least one of which has substantially uniformly distributed inductance and capacitance per unit length.

Another object of the present invention is to provide a broad band wave filter section comprising two impedance branches having reactive impedances of different frequency characteristics. which by their ratio determine the transmission characteristics of the filter, one of said branches having a section of uniform and substantially dissipationless transmission line. i

A further object is t'o provide a filter for high frequency waves employing a concentric type of transmission line.

A still further object is to provide a filter employing one or more tuned circuits having extremely low power factors and occupying relatively small space.

In my invention I provide, among other things, an inductance system made of a transmission line section composed of two hollow concentric metallic conductors or cylinders. By making the conductors coaxial and cylindrical, the current is constrained to travel in uniformly distributed manner over the outside surface of the inner conductor and to return in uniformly distributed manner over the inside surface of the outer conductor. In view of the fact that the lines of magnetic flux are almost completely contained within the space between the outer conductor and the inner conductor, the possibilities of any current losses are minimized, mainly because the space through which pass the magnetic lines of force constituting the flux is air. I also propose to combine a low loss capacitance with a concentric transmission line type of inductance to produce a tuned circuit having an extremely low power factor.

Other objects, features and advantages will appear from a reading of the specification, which is accompanied by a single drawing showing diagrammatically a filter circuit in accordance with the invention employing concentric transmission line sections as elements thereof.

Referring to the drawing in more detail, there is shown an electrical wave band pass filter employing low loss transmission line sections of the concentric type comprising elements I 04, I06 and I08, each of which may be as shown, or any of the transmission line sections described in my parent application of which this is a true division. The filter comprises a series impedance branch and a shunt impedance branch, the series impedance branch utilizing one or more condensers, as indicated, while the shunt impedance branch utilizes the concentric transmission line devices. Each concentric transmission line element of this filter comprises an outer conductor 4 and an inner conductor 2, both conductors being directly connected together by a conductor, such as a ring 6, at one of their adjacent ends. At their other adjacent ends condenser 8 is connected between the conductors 2 and i. In effect,

the concentric transmission line comprises an inductor which, in combination with condenser 8, may be tuned to a desired frequency. The filter arrangement may obviously be connected in such manner as to form either a high pass or a low pass electrical circuit. Moreover, it will be evident that any number of concentric transmission line sections of the type shown in the drawing may be used in the filter arrangement, and that combinations of different types of these concentric transmission line sections may also be used without departing from the spirit and scope of the invention. The filter shown in the drawing may also be duplicated by another similar system and so arranged that the conductor H0 of the other system coincides with the conductor N0 of the filter shown in the drawing, thereby providing a back-to-back filter arrangement.

It should be distinctly understood that the invention is not limited to the precise filter arrangement illustrated and described since various modifications may be made without departing from the spirit and scope of the appended claims.

What is claimed is:

1. An electrical wave filter comprising a wave transmission line of recurrent structure, the recurrent series elements of said line being composed of condensers, and the recurrent shunt elements being composed of transmission line sections having uniformly distributed capacity and inductance per unit length, the lengths and constants of the shunt elements, and the capacitances of the series elements being so proportioned with respect to one another that the electrical wave filter will have pass bands at certain desired frequencies.

2. A broad band wave filter section comprising two impedance branches having reactive impedances of different frequency characteristics which by their ratio determine the transmission characteristics of the filter, one of said branches comprising a section of uniform and substantially dissipationless transmission line having harmonically spaced critical frequencies in combination with a capacity.

3. A broad band wave filter section comprising two impedance branches having reactive impedances of different frequency characteristics which by their ratio determine the transmission characteristics of the filter, one of said branches comprising a section of uniform and substantially dissipationless transmission line having harmonically spaced critical frequencies in combination with a capacity, in which the capacity is connected in shunt with the line setion.

4. A broad band wave filter section comprising two impedance branches having reactive impedances of different frequency characteristics which by their ratio determine the transmission characteristics of the filter, one of said branches comprising a section of uniform and substantially dissipationless transmission line having harmonically spaced critical frequencies in combination with a capacity, in which the capacity is shunted across the input terminals of the line section.

5. A broad band wave filter section comprising two impedance branches having reactive impedances of different frequency characteristics which by their ratio determine the transmission characteristics of the filter, one of said branches comprising a condenser in combination with a section of uniform and substantially dissipationless transmission line of the type having two conductors arranged physically in parallel.

6. A broad band wave filter section comprising two impedance branches having reactive impedances of different frequency characteristics which by their ratio determine the transmission characteristics of the filter, one of said branches comprising a condenser in combination with a section of uniform and substantially dissipationless transmission line of the type having an inner conductor surrounded by an outer conductor.

7. A broad band wave filter section comprising a series impedance branch and a shunt impedance branch, said series branch comprising a condenser, said shunt branch comprising a second condenser connected in parallel with a section of uniform transmission line short-circuited at its distant end, and the impedances of said branches having frequency characteristics so proportioned with respect to each other that the filter Will transmit a certain desired band of frequencies.

8. A wave filter section comprising a series impedance branch and a shunt impedance branch, said shunt impedance branch comprising a section of uniform transmission line in combination with a condenser, and the impedances of said branches having frequency characteristics so proportioned with respect to each other that the filter will transmit a certain desired band of frequencies.

9. An electrical wave filter comprising a series impedance branch and a shunt impedance branch, said series branch consisting of a condenser, said shunt branch comprising a section of uniform transmission line, and the impedances of said branches having frequency characteristics so proportioned with respect to each other that the filter will transmit a certain desired band of frequenoies.

10. An electrical wave filter in accordance with claim 1, in which the shunt elements consist of two-conductor transmission lines.

11. An electrical wave filter in accordance with claim 1, in which the shunt elements consist of concentric transmission line sections.

HAROLD O. PETERSON. 

